This invention relates to a process for preparing an alkoxylated carbonate (i.e. polyether carbonate) product. This process simultaneously transcarbonates and alkoxylates a mixture of compounds with at least one alkylene oxide, in the presence of a mixture of catalysts. The present invention also relates to novel polyether carbonates.
A general review of the chemistry of polymerizing propylene oxide with carbon dioxide in the presence of a suitable catalyst to produce polycarbonate polyols is provided by D. Darensburg and M. W. Holtcamp in the article “Catalysts for the Reactions of Epoxides and Carbon Dioxide”, Coordination Chemistry Reviews, 153, 1996, pp. 155-174. Cyclic carbonate and/or polycarbonate synthesis via epoxides and CO2 is described, as is ring-opening polymerizations of cyclic carbonates.
Various processes have been used to prepare polyether carbonate polyols from alkylene oxides and carbon dioxide, in the presence of a DMC catalyst. One problem resulting from most of the processes is the formation of a high level of propylene carbonate which is an undesirable by-product of these processes. Efforts to overcome this problem include the combined use of a DMC catalyst with a co-catalyst, and the use of a substantially non-crystalline DMC catalyst.
In spite of the advances made recently in this area, there continues to be a need for alkoxylated carbonate products (i.e. polyether carbonates) with low levels of cyclic carbonate by-products, and new processes for preparing these alkoxylated carbonate (i.e. polyether carbonates) products. We have surprisingly found that reacting alkylene oxides with carbonates using a dual catalyst system offers a very efficient method for preparing polyether polycarbonates with very little formation of cyclic carbonate byproducts.